A flat, unmoulded fascia or string course, forming a horizontal band along a wall, a border around a window, etc.
2A fillet between the flutings of a column.
3A flat lintel over a door or window.
A narrow flower bed or strip of turf forming a border.
Late 17th century; earliest use found in Edward Phillips (b. 1630), writer and biographer. From plat + band, after French plate-bande.